This invention relates to flame-and smoke-retardant rigid polyurethane foam, and more particularly to 2-trichloromethyl-1, 3-oxazolidine, 2-trichloromethyl-1, 3-thiazolidine and derivatives thereof which are especially useful in retarding smoke and flames in rigid polyurethane foams.
Rigid polyurethane foams are becoming increasingly important as an insulation material in construction of new buildings to reduce energy losses. Building code regulations now require that these foams be not only flame retardant but also have low-smoke properties in order to make escape exits more easily observable by the occupants and to allow easy access by firemen. The prior art discloses the use of chlorinated compounds as flame retardants such as trichlorobutylene oxide for rigid polyurethane foam but these compounds have the disadvantage of generating too much smoke on combustion of the foam. (See U.S. Pat. No. 3,741,921). The flame and smoke retardants of this invention overcome the disadvantages of the prior art because they generate less smoke on combustion.